The invention relates to positioning read/write heads in disc drives. In particular, the invention relates to microactuators that are used to position read/write heads in a disc drive.
Disc drive heads are typically positioned by the combined action of a voice coil motor and a microactuator. The microactuator is typically located at the distal end of a suspension and provides a smaller amplitude, but higher bandwidth lateral motion compared to the lateral motion provided by the voice coil motor. Various types of feedback from the microactuator to a controller have been used to improve control of the microactuator position.
Magnetic velocity coils have been used to provide feedback from microactuators, but these coils provide only an indication of microactuator velocity, while the relative position of the microactuator is not available to the controller.
Capacitive sensors have been used in microactuators to provide feedback of relative position outputs, however, there are problems with capacitive sensors. The electronic sensing circuitry for capacitive sensing is mounted to the disc drive housing and leads are run between the capacitive sensor and the sensing circuitry. The leads introduce stray capacitance and noise, making the sensing inaccurate. In order to overcome the problems with inaccuracy, capacitive sensors are used that have large sensing capacitances. In order to achieve these large sensing capacitances in the limited space available in a microactuator, complex, interleaved grooved structures are etched. The grooved structures are expensive and time-consuming to micromachine and difficult to align.
There is a need for a microactuator with a capacitive relative position sensor, and associated capacitive sensing circuitry, that can be produced at low cost and provide a relative position output that is accurate in the presence of noise and stray capacitance.
Disclosed is a microactuator for mounting on a suspension for positioning a read/write head in a disc drive. The microactuator comprises a first microactuator component having a mounting surface adapted to mount on the suspension, and a second microactuator component having a mounting opening adapted to receive the read/write head.
The first and second microactuator components include corresponding first and second insulating deposits that are flat and spaced apart from one another by an air gap. The first and second insulating deposits are laterally movable relative to one another responsive to a microactuator electrical drive current.
The microactuator also comprises first and second drive electrode deposits that are flat and interdigitated. The drive electrode deposits have corresponding first and second contact pads adapted to receive first and second electrode drive voltages. A sense electrode deposit is flat and digitated. The sense electrode deposit has a sense contact pad providing a relative position output. The drive and the sense electrode deposits are disposed on the insulating deposits with the sense electrode deposit facing both the drive electrode deposits across the air gap.
These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.